Great attention has been paid to optical disks as high capacity information carrying media. Optical disks are generally classified into optical recording disks and read only optical disks. The optical recording disks include rewritable type disks such as magneto-optical recording disks and write-once type disks such as pit formation type optical recording disks, and the read only optical disks include laser disks (LD) and compact disks (CD).
In general, these optical disks comprise a recording or information carrying layer on a substrate. The substrates are often formed of resinous materials, typically polycarbonate and acrylic resins because of light weight, ease of handling, and low cost. The resinous substrates, however, are susceptible to damages or scratches due to their low hardness. Since optical disks are generally recorded or reproduced by directing light through the substrates, damaged or scratched substrates can impose difficulty to the information recording and reproducing operation.
It is then desired to form a hard coat layer on at least the light incident side of substrates for protection against damages and scratches. Such hard coat layers on the light incident side of substrates are known, for example, from Japanese Patent Application Kokai No. 165050/1989 disclosing UV cured films of oligoester acrylate-containing composition. These hard coat layers or UV cured films have a surface resistivity of about 10.sup.15 .OMEGA. and are thus susceptible to electrostatic charging. Once the hard coat layers are charged, dust and debris will deposit on the hard coat layer surface, causing errors to occur during recording and reproducing operations.
Attempts for rendering the disks antistatic have been made, for example, by forming a hard coat layer from a surfactant-containing composition to thereby reduce surface resistivity or by forming an antistatic film on a hard coat layer. However, the hard coat layers of a surfactant-containing composition are still insufficient in antistatic effect since they have a relatively high surface resistivity of about 10.sup.11 to 10.sup.13 .OMEGA.. The double coating method of forming an antistatic film on a hard coat layer is less efficient in mass production and leaves a problem with respect to the continuity of antistatic effect.